Most people don't get Schrodinger's Cat (including you?)

[@LookingGlassUniverse]

The second cohort for the live version of this course is now open! The 4 week live course will run from Jan 6 - 31st 2025. The lectures will all be free and available on youtube, so the course is just for those who want to go a bit deeper by doing homework problems, a weekly tutorial, and asking questions. If that sounds interesting to you, there's more information here: looking-glass-universe.teachable.com/p/quantum-mechanics-fundamentals1

[@holemajora598]

When a photon is jettison from whatever is glowing, it shoots off in a random direction. If the photon were to be spinning, regardless of orientation as it is randomly shot off of the parent material wouldn’t then the photons traveling in any one direction also be randomly oriented in their rotation? I mean, if we could dictate the direction a photon came off of a material our laser technology would increase exponentially. Aren’t lasers essentially polarizing the direction of their photons through the crystalline structure of the lazing material.

[@TimoBlacks]

@@holemajora598 Your mistake is thinking that the photon is travelling.

[@sergeynovikov9424]

the Schrodinger's Cat cannot be isolated in a box of any kind from its observer -- therefore the cat and its observer are staying in connection with each other all the time. your statements in the video about the Schrodinger's Cat are absolutely wrong, sorry.

[@chrisevans1255]

Schrodinger used the cat thought experiment to illustrate how WRONG it was. The cat is not superpositioned. This was the entire point.

[@TimoBlacks]

@@chrisevans1255 you are exactly correct.

[@F16_viper_pilot]

Your light experiment at 12:00 only proved to me that two filters aligned in the same orientation will expectedly allow all the same polarized light through that was polarized by the first filter. You turned both filters 45 degrees so they were still aligned. There’s no mystery there and it doesn’t speak to quantum physics.

[@kurtreber9813]

So true! This didn't prove anything other than the results are the same when the filter is the same RELATIVE to the light.

[@rcanoli99]

I agree but I think you mean just before 13:00 No great surprise when the light is aligned to the filter - 45 or any angle - all the light passes thru ...

[@robertwilson2007]

Yes I was yelling at the video. What the F are you talking about lady? The light is still aligned with both light and filter at 45 degrees, of course it will be at 100%. Does she have any clue to what she is talking about?

[@robertwilson2007]

Yes I was yelling at the video. Lady what are you talking about? The light and filter are both aligned at 45 degrees to give 100% of the light. Does she have any idea what the hell she is talking about? I know I am stupid but come on man !!!

[@igNights77]

Schrodinger's Cat recently went on a crime spree He's wanted dead and alive

[@benhoffmann6870]

Yes - but if he's wanted dead AND alive, why is he wanted? You already have both those states. Therefore, a cat can get away with anything

[@michaelprozonic]

@@benhoffmann6870 and always does

[@xmillion1704]

At least he’s landed on his feet.

[@prashanthramg9005]

13:00 - If the laser is 45 deg aligned and filter too is 45 deg aligned (to the white surface) the whole light passes through. This is just as expected... what's surprising and why... Real surprise happens when you insert a second filter infront of the first at a 22.5deg angle. Now intuitively we guess light would dim but actually it brightens (sqr(cos 45) = 0.5 and sqr(cos 22.5)*sqr(cos22.5) = 0.728)

[@Kakazumba99]

The same thing I was thinking but I would guess I am missing somethimg. Maybe someone can hop in and explain

[@cmfortblynumb]

@@Kakazumba99 I don't think anyone can explain that, I would assume it's just a confusion.

[@mad_vegan]

If you're thinking about light as a continuous wave, those results are exactly what you'd expect. But light is not continuous, it's quantized. Unfortunately, she failed to mention that those experiments are only surprising after you take that into account. If you decrease the intensity of light, you notice that a vertically polarized photon has 50% chance of passing through a 45º filter. The intensity of each photon is the same, only the probability of passing through is reduced. If you measure it again, you find that each passing photon has 50% chance of being in the same polarization and 50% of turning into a horizontal one. With a second filter, you'd expect 50% of each to pass through, but this time it's different -- all of them pass through.

[@siarez]

The increase in brightness after insertion of a second filter at 22.5deg is also explained by Maxwell, and doesn't need quantum physics. To prove anything quantum mechanical is going on, you should shoot one photon at a time. That's only when Maxwell's EM produces a different prediction than quantum mechanics.

[@peetiegonzalez1845]

This proves, via Bell's Inequality theorem, that the light that made it through the 45° filter didn't do so because it had some hidden state that gave it a certain probability of getting through that angle, and the probability of going through the next filter at a different angle was based on that hidden state... but that going through it actually gave it a property that makes the probability of going through a different polarisation dependent on the new state.

[@AT-27182]

The observer might not know the state of the cat before opening the box, but I am pretty sure that the cat knows its state before the observer opens the box.

[@ChalkyWhiteChalkyWhite]

tell the cat to publish its findings

[@santiagomoebio]

What you have there is a superposition of a cat that knows its state, and a cat that's dead. The "knowing" belongs to the states. If the decaying particle triggers a red light instead of killing the poor cat, and indeed it's not a cat but a scientist, you have a superposition of a scientist that knows the particle decayed, and a scientist that knows the particle didn't decay.

[@LookingGlassUniverse]

It annoys me that people think a cat wouldn’t count as an observer

[@santiagomoebio]

@@LookingGlassUniverse the cat (and the decay detector) are observers, and thus collapse the particle quantum system they observe, but if they (particle, decay detector and cat) are informationally isolated from the outside of the box (the premise of the experiment), they as a system are in superposition, because nothing outside has measured them.

[@MiteshJethawa]

​@@santiagomoebio The Thing is You can Just Say That To Yourself, If you saw a Particle Decayed in The Laboratory But The Laboratory is Isolated From The World Because Radiation would Leak So The Laboratory is In Superposition right?

[@Ameise2]

13:10 I don' t get it. Isn't that measurement at 45 degree the same as the first measurements, where the light source and filter are aligned the same? It is just tilted. What am I missing here? Can someone explain?

[@randompastahandle]

Ya, I rewinded this bit a lot of times and I have no idea how she thinks light works in the alternative theory but the obvious one has all of the light going through either way.

[@3SPR1T]

The first filter aligns all photons in one direction. If the 2nd filter is horizontal all light gets blocked. If the 2nd filter is vertical all light gets through. Now what says that about the light? It should be 100% vertical, by that logic. Now why is 50% getting through at 45°? It is because the light is in both positions at the same time until we let it pass through the 2nd filter.

[@AnonymousAnarchist2]

Its more covering bases the important thing to know is If the light was polorized at a set angle and just at that angle, then only equal angles within 180° measures would allow light through at all. I.E. the polorized filter at 45° should block all light from either up or down, because that filter is just a bunch of lines spaced so close other light waves cannot get through, usually like 400 nn spaces between each line. That means there must be something else going on

[@Danyel615]

TLDR: You are not missing anything. It is the same other than being tilted, so this is not exactly a proof in favor of quantum mechanics. Longer answer: It does suggest, that a superposition (coherent mixture) is *NOT* the same as just not knowing which state it is (incoherent mixture). That is true both in classical physics and in quantum mechanics. I think this gets to a misconception about QM: superposition by itself is not a strictly QM phenomena. Anything that follows a linear differential equation will satisfy a superposition principle. You can have a superposition of classical electromagnetic waves for example, or heat waves. The Schrödinger equation is linear, so you can also have a superposition of wavefunctions as well. If somebody tells you a system is superposed, that is not enough for you to know if it is a quantum system or not. You have to do further tests and check: if it is superposed in its outcomes, then it is classical. If it is superposed in its possibilities, then it is QM. In fact, this whole experiment is not strictly speaking a proof of QM. You can fully explain it using the superposition of classical EM waves. To put it simply, Maxwell would not get surprised by these results! If anything, this polarizer experiment gives credence to the idea that light is a wave. Classically, you would predict that if the laser is in +, and the polarizer measures +, then all of the light will go through (100%), and none of it if it is antialigned (-). If the polarizer points along H or V, then half of the light will go through (50%). On the other hand, if the laser is depolarized, then you'll get half of the light through no matter the orientation of the polarizer. From a QM point of view, if the laser is in |+>, and the polarizer measures + (P_+ = |+>) = 1). If it is antialigned(P_- = |->) = 0). If the polarizer is along H or V, the light will go through only half of the time (Tr(P_H|+>) = 0.5 and Tr(P_V|+>) = 0.5). If the laser is depolarized (and thus it is in the state rho = 0.5*(|H> through an H or V polarizer, you would expect "half" of the photon to go each time. But we have never seen that. All of it goes through, but it goes either without a pattern if you repeat it many times. To be even more strict, the Poincare sphere maps one to one with a one-qubit Bloch sphere (see for example doi.org /10.1023/A:1018703709245), so you cannot fully convince yourself of QM effects even if you stay at the single photon level on polarization only. You have to at least make the single photons interfere to see anything of the weirdness (like a Michelson single-photon interference), and even then is not enough for the sticklers. The real head-scratching effects can only occur once you have at least two photons, either if you entangle them and check for Bell inequality correlations, or if you do two-photon interference and check for the HOM effect. The laser pointer has too many photons and a g2 =1, so unfortunately you cannot really use it to prove QM effects. I know this is an analogy but even in the analogy it doesn't work because it leads you to think that the three polarizer paradox is somehow a mysterious QM effect, but it is not (it is just that adding and subtracting with vectors is a bit less intuitive than using just plain numbers). Sorry for the long answer!

[@Ameise2]

Thank you all for the explanation, very helpful! @Danyel615 had to go through it a couple of times, thank you very much for the detailed answer!

[@wonderfulworldofmarkets9033]

Hi I posted a few years ago about how I was a bad student all my life and thought I was dumb. And watching your channel taught me how interesting STEM can be and you motivated me to go back to school. You responded and told me to keep you updated! So here I am! Since then, I graduated my Computer Science Bachelors of Science with a perfect 4.0 GPA. I got all A's in every single subject for all 4 years. It was insanely hard but I just worked harder. I also got a job at a FAANG company earning way too much money and am dating the girl of my dreams and about to propose to her :). My life is litterally a dream I couldn't have imagined 5 years ago when it felt like I was doomed. Thank you for creating these videos and motivating people like me!

[@Klayhamn]

sheesh.

[@LookingGlassUniverse]

Oh my goodness… that’s incredible!! Well done on your hard work, it’s clearly paid off! It’s your own work that got you to this point, and I’m so impressed and proud of you. Thank you for updating me, I’m so happy to hear it ❤️

[@al2642]

A further misconception. The cat in the box will be dead or alive at any given time. The collapse of the wavefunction does not happen when you (awareness) look, but in the interaction between cat and atom. The macroscopic non supeeposition remains valid even in schrodinger cat. Because the observation is the interaction of cat and atom. The observer is in the same situation of the rejection letter. In other words, the moon still exists when you do not look. Not because supeeposition is not valid, but because supeeposition and wave function collapse are happening between moon and the rest of the universe. You can look or not, know or not, but that moon is still there. The misconception is assuming the awareness of the human brain is the key. It is not. The observation I s the interaction between cat and atom and all else. This makes the cat only dead or only alive, because it is macroscopic.

[@amihartz]

That is not quantum mechanics, but an objective collapse model which makes different statistical predictions. In traditional quantum mechanics, the reduction of the state vector is not a physical process, it is merely updating a probability distribution based on new information acquired, so it is relative to the information accessible from a particular frame of reference. It is not a physical event that occurs in objective reality. This is incredibly important because what you are advocating is a fundamentally different theory that makes different predictions. In traditional quantum mechanics, you would describe the particle as becoming entangled with the detector, and this combined system further entangled with the cat in a tripartite system described by a single wave function. Because it is described by a single wave function, the whole combined system taken together could in principle exhibit interference effects in subsequent interactions. What you are arguing is instead that the reduction of the state vector is a physical event that occurs in physical reality when the cat interacts with the atom, and thus interference effects would not be in principle possible for the combined system of the cat, detector, and particle taken together. This is a quantifiable different theory because interference effects are directly observable, well, quantifiable, it makes different predictions. It's also simply not even possible to reproduce the predictions of quantum mechanics if you claim that the particle's wave function collapses as a physical event with every interaction, because then interference effects would not be observable at all. You thus need to posit some sort of "threshold" as to what _kinds_ of interactions are "special" such that they suppress interference effects. Anywhere you draw this line, anywhere you set the threshold, would give you different statistical predictions that deviate from traditional quantum mechanics. Quantum mechanics, as it is currently formulated in the common literature, simply has no threshold at all. Interference effects could be in principle scaled indefinitely. Issues such as decoherence which dilute the effects into the environment, as well as the de Broglie wavelength being smaller for more massive objects, makes it difficult observe them on large scales, but are in principle there. Again, what you are proposing is simply a separate theory from traditional quantum mechanics which makes different predictions, what is known as an objective collapse model, and such a model requires you to specify the actual threshold here, what kinds of interactions actually qualify as one that would lead to a physical "collapse" of the wave function.

[@adriaancanter4573]

13:30: You've just re-demonstrated 100% transmission when the polarity filter directions are the same just as you did earlier in the video. You should've emphasized this (intentional sleight of hand?) more - the fallacy of thinking of the filters as something that "block" light just in one direction, in the conventional sense. Minor nit - I don't think it's fair to call Schrodinger wrong because he wasn't arguing for ultimate determinism, he was directly criticising the "standard" interpretation as you call it (i.e. the Copenhagen Interpretation aka "shut up and calculate") in particular for it's reliance on classical observers and instantaneous wave function collapse. The absurdity he was pointing out remains a point of confusion and debate, well after the reality entanglement has been verified. I think it's safe to say there is no "standard" interpretation today, thanks.

[@BenjaminGatti]

@@adriaancanter4573 there is no 100% transmission in a real experiment. This fact will become important when you compare it to bells inequality.

[@amihartz]

Schrodinger later in his career adopted a position similar to relational quantum mechanics. He initially hated Heisenberg's initial formulation of quantum mechanics which did not use a wave function at all (not many people know you can formulate quantum mechanics and make the same predictions without the wave function, which makes it odd when people "take the Schrodinger equation seriously" because it is purely a result of an arbitrary choice in mathematical formalism). In Heisenberg's matrix mechanics, rather than continuous evolution of a wave, as Schrodinger put it "electrons hop about like a flea" from interaction to interaction. He had hoped his wave equation would "fill in the gaps" between these "hops" and provide continuous and smooth transition of one state of a particle to the next. However, if you read some of Schrodinger's later writings, he entirely abandoned this position. He argued that the wave equation did create a smooth transition between interactions, but introduced a new discontinuous jump, a "gap," whenever you make a measurement, and he could not see why measurements should be important to a theory at all. Of course, the video publisher supports the Many Worlds Interpretation (a multiverse), but Schrodinger took a more deflationary route. He argued that we should just abandon continuous evolution and accept that what is ontologically real is only the particle in the moment of interaction and there is no continuous transition at all. He referred to this continuous transition as the "history" of the particle and argued that the particle simply has no complete "history" as any time you try to establish one will find there are "gaps" in this history that is impossible to fill. For example, how quantum mechanics is commonly presented on KZbin is that the photon splits into a wave and "takes both possible paths" and then "collapses" at the detector to a single outcome. Schrodinger believed that instead we should think of it as the photon only exists relative to something it is interacting with, so it exists relative to its interaction with the laser that produced it and relative to the detector it lands on, but if you ask where or what the photon was doing in between the two interactions, it is a category mistake. The photon does not have meaningful existence as an autonomous entity. It's not spreading out in both possible paths, it really does "hop about like a flea" from the laser to the detector. Indeed, when he presented the famous "Schrodinger cat" thought experiment, his purpose was very specifically to criticize the notion that particles actually spread out as waves, what he called a "smeared out" or "blurred out" state depending upon the translation of his paper. His argument was a reduction to absurdity: if particles can become smeared out, then a cat could become entangled with a system from a smeared out particle through a chain reaction, which would then require you to include the cat as part of this smeared out state. Nobody can possibly believe a cat can be smeared out, so no one should believe particles can, either. That was, of course, _his_ reasoning, but people often present his thought experiment as if he was arguing _in favor_ of cats existing in a smeared out state.

[@Kevin-ht1ox]

Perhaps I am not smart enough but I see the two polarization filters aligned and all the light passes through. How does that demonstrate superposition? Am I smoking something?

[@BenjaminGatti]

@Kevin-ht1ox it doesn't demonstrate much.

[@jefferybridgland9907]

This was definitely sleight of hand! When you have rotated the axis of the light and the axis of the filter,by the same amount nothing has changed. That was silly.

[@ExcretumTaurum]

To paraphrase Sir Terry Pratchert: “the cat is either Dead or Alive And Bloody Furious”

[@Martincocina-lx5tz]

Totally wrong experiment with the filters, when they are aligned who cares if they are at 45 degrees or whatever the value. are just aligned in the same axis. Very strange mistake

[@jr.bobdobbs]

Yes, it is incorrectly presented. She should redo the video.

[@peetiegonzalez1845]

In the context of having tested that same light for vertical and horizontal polarity. She's kinda working backwards but it's not wrong.

[@cmfortblynumb]

@@peetiegonzalez1845 I don't think it makes any sense, I would assume it's just a confusion

[@tedr.5978]

The polarized filter demonstration in this video is wrong.

[@kipper1668]

Lyle: To me, the laser experiment breaks down at the assumption that the light must be made of either horizontal or vertical light. To me it seems a much more straightforward explantion that when the filter is at a 45° angle, so is the light, and the amount that gets through is based on the relative alignment of the filters, in which case all the light passing through in the 45°-45° case is completely expected, ss well as none of it in the 45°-135° case. The math section was surprisingly clear and helped me see how superposition is a very practical mathematical convention, but I don't see how it's necessarily anything more physical than that. In the double slit experiment, the interference pattern would be the same if you did it with waves of water, right? In that case you very clearly have more than enough information about how the waves are travelling. It makes sense to us that interaction from any kind of physical system can collapse a suoerstate. It seems presumptive to say it has to do with consciousness, and we generally have a pan-psychist worldview and would argue that it's not an absurd idea that all phenomena has its own kind of consciousness, anyways. I am, however, confused about what would constitute a "measurement" versus any general kind of interaction. Don't all interactions constitute information about the phenomena involved? Just because we can't decode it from our perspective, if sonething happens, shouldn't there be _some_ perspectives through which its qualities can be known? If there are truly ambiguous states, then any theory about the nature of them would be necessarily completely arbitrary, since if it provides some way to learn about that state, and then the state is no longer ambiguous, insofar as what was learned about it. There must be something to this, since things like quantum computing have had some success, that must mean that there ARE some physical and meaningful qualities to superpositions, if they can be used directly to unique effect. This video was, I think, very well put together and helped us feel a lot less confused about quantum mechanics, especially the math portion. I just still don't understand how the superposition would be necessary or real on more than a mathematical level. I look forward to learning more, though! I think the way you're going, this chnnel will only do more and more for helping non-physicists understand Quantum Mechanics, keep up the good work!

[@BSJDynasty]

this! I was about to type the same thing, the physical light experiment really doesn't prove anything at all.

[@Miguel_Noether]

Don't overthinking it, it was just a demonstration of linearity (and superposition as a consequence), one of many characteristics of quantum mechanics

[@kipper1668]

@@Miguel_Noether What is linearity?

[@GoodWill-s8j]

​@Miguel_Noether the point is: it failed to explain the claims.

[@davidf2281]

@@Miguel_Noether It wasn't a demonstration of anything at all.

[@platypi_otbs]

The objective of the experiment at 13:00 isn't clear. What I see is that you put a 45° filter in the path of 45° light and it doesn't block the light. How does that show results that prove superposition? [edit] I rewatched it. All this experiment shows is that if you rotate the entire experiment it behaves in a consistent manner

[@BenjaminGatti]

Polarizers are not filters, they are operators. If polarizers were filters, they would either block 99.999_% of the light if they were perfect or they would be imperfect. Instead, they operate on the light to create altered light states. The operation is basically to rotate the incoming light by the inverse of theta such that the resulting light has theta 0, and to modulate the probability amplitude by cos(theta) such that the probability of transmission is highest for photons that are rotated the least. The word "filter" is the problem.

[@JrgenMonkerud-go5lg]

yeah that is also what a filter is though. operator is a mathematical concept, the filter is a bunch of matter or something in the real world, the math, is not, the real world.

[@BenjaminGatti]

@JrgenMonkerud-go5lg Cambridge dict: "a thin piece of plastic or glass placed in front of a camera lens in order to change the color or amount of light entering it:" in all cases the word, initially felt used to remove particulates from water, implies primarily the absorption of the undesired. In no usage does it imply altering that which is passed. And a polarizer first and foremost applies a rotational operator of -theta to that which is passed. To understand this is to understand the 3 polarizer demonstration. It does not "pass" any light unmodified. Therefore it is a light modifier, more like a lens, than a "filter". Language is simply wrong where it reduces comprehension. This is such a case.

[@JrgenMonkerud-go5lg]

@BenjaminGatti i don't care about a dictionary, those are written by people who don't understand physics. I'm not saying you are wrong about the name of a mathematical representation of what a polerizer does. I'm saying that we don't know what "it" or "does" really means in nature. We have mathematics sure. But i don't see why the dictionary has anything to do with it.

[@JrgenMonkerud-go5lg]

@BenjaminGatti i know how they work mathematically broski. I know a bunch of different models for how they work in nature, including as an operator. But it is a crude picture dude, it isn't realistic, even if it produces the correct statistics.

[@BenjaminGatti]

Ok. I think we agree largely on this. What are your thoughts on EPR -> Nobel 2022?

[@michaelbourrell2693]

No cardboard boxes were harmed in the making of this video.

[@obsidianjane4413]

You were doing so well until @1:15. "Schrodinger's Cat" wasn't an explanation of superposition. It was a criticism of trying to extrapolate a literal meaning from probabilistic distribution. Like misrepresentation and misunderstanding of the wave function in a double slit experiment.

[@TimoBlacks]

Close but incorrect. Schrodinger was not criticising the "trying" for a literal meaning. There was no need for him to criticise such a "trying", because nobody was "trying". Back then, it was all Bohr's interp. Which was DONT EVEN try --- to picture things, there IS NO picture, in the first place. The project of physics reached a limit at this scale, can't think of particles as existing independent of measurement. That was QM back then. Hence, there was no need for S to criticise this "trying" to picture things. Whose trying was he criticising? His own? Nobody was trying. The reason S brought up the cat was to help CONVEY the bizarre-ness of quantum theory. He was making it relatable, by connecting it to something familiar, something that can be pictured --- a cat. If he (as you claim) wanted to discourage picturing things, why would he INVENT a picture -- of a quantum system spreading its magic to the macro scale? That would defeat his own purpose.

[@obsidianjane4413]

@@TimoBlacks You rambling post does not contradict mine. So... I don't know what you are trying to say here. 2nd sentence is false.

[@TimoBlacks]

@@obsidianjane4413 Simply your correction was wrong. That simple. Learn the facts.

[@obsidianjane4413]

@@TimoBlacks Bad translation maybe? Pendant too much? Donno. Don't care. Bye.

[@TimoBlacks]

@@obsidianjane4413 If you don't care, then don't ask the question. Not too bright are you? Kind of like earlier, you saying that nothing i said contradicts you _while also_ saying that my second sentence is wrong. If it was wrong, then it was (in your mind) opposite to what you were saying, which means it DOES contradict you. No need to be offended. If you want to go around correcting people, then be ready to get corrected too :)

[@brothermine2292]

The "proof" is flawed, because it fails to rule out the case where the light that passed through the initial 45º filter is all at 45º. This case seems the simplest, most straightforward explanation. The "superposition of 0º and 90º" merely predicts what would happen if 45º light passes through a second filter that's oriented at 0º or at 90º. The superposition does NOT imply the light is at 0º and 90º _before_ it reaches the second filter. It wasn't until Bell's Theorem about two entangled particles that it was proved that Einstein & Schrodinger were at least sometimes wrong about their belief that quantum mechanics was incomplete due to ignorance of the values of local hidden variables. Bell's Theorem didn't falsify hidden variables nor establish that quantum mechanics is complete; it only falsified the hidden variables theories in which all hidden variables are local.

[@TimoBlacks]

"Bell's Theorem didn't falsify hidden variables..." blah blah simplified: "the theorem did not show there are no hidden variables; it showed there are no local ones!" so you are saying there COULD BE non local hidden variables. philosophic bs. just another day of playing with the ways that words can be joined. Oh look! i can put the word NON before the word local. So... i open an opportunity for spin to be determined! because it's not limited to being determined by a LOCAL process!... because there is always this NON local one! ya don't even know what it MEANS for a deterministic process TO BE non local. it's just word games. just philosophers doing their _usual_ loiter then acting like they have important physics news. this is why yall are disliked by us. because yer out to lunch AND cannot notice that you are. the Theorem falsifies all hidden variables because the variables _you_ think exist don't.

[@brothermine2292]

>TimoBlacks : How did you come to believe nonlocality -- in particular, nonlocal hidden variables -- is impossible? No one yet has such a good understanding of space & time that the Locality axiom ("nothing can be influenced by anything outside its past lightcone") can be proved to always hold. Even Einstein, who championed Locality and included it as an axiom (named Separability) in the 1935 EPR paper, showed in the 1935 ER paper about Einstein-Rosen bridges (aka wormholes) how General Relativity can violate Locality. Bell's Theorem proved that a set of "common sense" axioms is inconsistent. That implies at least one of those axioms is wrong. Which axiom(s) do you think is(are) more likely to be wrong than Locality, and why? People who spout opinions about the world but can't support them with evidence or reasoning, like you apparently, are a bigger problem than the people you want to whine about. They clutter the internet with biased opinions.

[@TimoBlacks]

@@brothermine2292 It is a contradiction of terms, that's how I know. You're late to (reality) party. if you want to claim that there CAN be a non local deterministic process, then you OWE (if you don't want to be laughed at) to show at least 1 such way (of the presumably hundreds of ways you think exist) that a NON local deterministic process could play out. But you can't. Not even just 1 possible way, can you show. because even you (who insist that such a process can exist) have NO CONCEPT what that even means. Hence philosophic bs. you are doing nothing different than someone who goes around claiming that a sphere CAN exist independently of that it's edge is a curve. The fact that you DO go around thinking so, is not a support that it's true. It supports that you cannot notice a contradiction of terms when it's right in front of you. Again, the only way you can convince me (or yourself for that matter) that there IS such thing capable as a NON local deterministic process, is to show 1 example of how that could (not how it does, but just how it could) play out in practice. Show me that you are sincere in your own claim. You can't do it. You can't even FATHOM a deterministic process by which this particle becomes spin UP (instead of spin down), except by thinking in LOCAL terms. As one cannot fathom how a sphere could be made of straight lines with right angle corners. It's funny because you (philosophers) even have a clue right in front of you that you are on the wrong track. The clue is your _own_ awareness that you cannot even FATHOM an example of what you speak. Cannot fathom the meaning of your own words. And yet you still persist pushing those words. That's what makes a philosopher.

[@brothermine2292]

>TimoBlacks : First, we note your addition of "deterministic" to your unsupported argument against nonlocality, where you ask for an example of a nonlocal deterministic process. Why are you insisting that nonlocal processes must be deterministic? Another bias, I presume. Second, an example is the deBroglie-Bohm interpretation of quantum mechanics. which is both nonlocal & deterministic. Third, when you ask for a "process" you're going beyond physics to metaphysics. That's also necessary for "processes" of local theories, since the equations of physics only tell us what we will observe or may observe given a set of conditions... we don't observe processes at the smallest scales. You haven't described any local process (let alone a local process that's deterministic), nor clearly defined what you mean by "process." Fourth, your analogy that a sphere can't be independent of its "edge" (by which I assume you mean its surface) is faulty. It's a geometric definition, which isn't a good analogy for knowledge about the world. Unless you think Locality can be proved by math... if so, let's see your proof. You neglected my question to you about which of Bell's set of inconsistent axiom(s) you think is more likely to be wrong than Locality, and why you think so. It's a fair & relevant question, since you claim Locality can't be wrong. Your claim that I'm "late to the Reality party" doesn't make sense, for two reasons: (1) The Reality axiom ("properties of things have values before they're measured") and the Locality axiom are two of the axioms in Bell's set of inconsistent axioms, and questioning whether the Locality axiom should be discarded has _always_ been about the possibility of preserving the Reality axiom in the correct description of the world. (2) I'm not a member of a party. I'm agnostic about which axiom needs to be discarded to achieve consistency, and the reason why I'm agnostic is that no one has offered a compelling proof that identifies which is the right axiom to discard. (You've offered only your bias, not a proof. If there were a proof, it would have won a Nobel prize.) If you think my discussion of Bell's Theorem implies I believe in nonlocal hidden variables, your reading comprehension is poor, since a claim that something hasn't been falsified doesn't imply the stronger claim that it's true.

[@TimoBlacks]

@@brothermine2292 Do you understand what process means? It means that 1 event is connected to another event, to another event, to another event, etc, by time etc. Else not a process. Which is to say -- the sequence is determined, SET together, by virtue of that connection existing (process existing). Smarten up. If you want to claim that there CAN be a non local deterministic process, then you OWE (if you don't want to be laughed at) to show at least 1 such way (of the presumably hundreds of ways you think exist) that a NON local deterministic process could play out. Also, I never once argued against non-locality. I argued against your word-salad, that there can be a NON local deterministic process. Smarten up.

[@Leemccuaig]

It was a device used to point out that quantum physics isn't a direct representation of reality, pretty simple really.

[@brightsideofmaths]

Most people forget the dots in Schrödinger's Cat as well :D Nice video by the way :)

[@peetiegonzalez1845]

tbf the transliteration in English is Schroedinger because we don't use umlauts. But we generally just end up spelling it the German way with neither umlauts nor the 'e' adaptation. Here we go trampling over each others language. lol

[@brightsideofmaths]

@@peetiegonzalez1845 I was not so serious but I had to point it out because I am not used to see the name "Schrödinger" written like this :)

[@BruceKoerner]

The fundamental mistake in this video is the assumption that quantum systems can only be in discrete states. There is no evidence I know of for that. Rather the quantum behavior arises because those discrete states are the STABLE states.

[@mskiptr]

If the measurement device is isolated well enough, it will only "collapse" the wave function for itself. Or in other words, if you carefully measure whether it is in a superposition of both measurements, you will find that it is.

[@elfofgreece423]

It's a example of the insanity of projecting quantum realities onto a macro scale. Schrodinger's cat is an absurdity, but somehow quantum mechanics physically allows quantum superpositions.

[@garyha2650]

Glad you said it. More like Schrodinger's troll, mocking convention, and throwing in an equation with an imaginary number as a joke. By my calculations, they bring imaginary results, but did he realize it would stall physics for decades? Anyway, what I'm saying, since science isn't a religion (or is it) ... is we would do well to distrust everything that led to the current stall. Any true scientist has the unenviable task of doubting everything he thinks. So have a nice day and toss it out. Re-evaluate, think outside the catbox. Since I could be wrong, someone tell me, what practical thing in the world has Schrodinger produced?

[@calibandrive7487]

I wish that the so-called "real numbers" had instead been named something like "medial numbers" or "linear numbers", and that the so-called "imaginary numbers" had instead been named something like "lateral numbers" or "orthogonal numbers", so that people wouldn't incorrectly assume that "real numbers" were somehow really real things, whereas "imaginary numbers" were somehow just figments of the imagination. In mathematics, the so-called "real numbers" and the so-called "imaginary numbers" have the exact same ontological status. They are both just numbers. The difference between them is that they are perpendicular to each other.

[@abhijithcpreej]

​@@garyha2650you think the imaginary number in Schrodinger's equation is a troll? Also if you want Schrodinger's contributions to science a simple Google search will suffice. To be more concrete: the complex number in Schrodinger's equation is a consequence of wave mechanics; Schrodinger himself did not realise it, but what his equation was describing was the probability of measurement (Born rule). The probability is obtained by squaring the coefficients of each possible state, wherein the imaginary number acts as a "destructive interference".

[@mskiptr]

@@calibandrive7487 Indeed! "Imaginary" numbers are no more unreal than negative ones. You could absolutely do without them, but they are convenient and can nicely describe various mechanisms found in nature.

[@wormalism]

It's a single quantum particle that triggers the release of the poison. The thought experiment is pointing out that you can't wave away the weirdness by saying it's just nanoscale particles. The Copenhagen interpretation has to have the cat in a superposition of being alive and dead. Cats are made of quantum particles too.

[@eitherrideordie]

Can 2 light waves cancel each other out perfectly? And if so where does the energy go?

[@tnb178]

An interesting experiment is if you place e.g. 9 polarization filters behind each other, each rotated 10° from the one before. With this setup you'll have rotated the polarization by a total of 90° without losing a lot of the light's intensity.

[@erikziak1249]

You will loose a lot of the light by that way! But some of it will pass through. A very little fraction. Still more than zero.

[@tnb178]

(cos^2(10*pi/180))^9 = 75%

[@jonathanholmes6285]

50% light through a 45deg polarizer or sqrt(2)/2?

[@mskiptr]

The experiment as presented in the video appears to assume light can _only_ be polarized horizontally or vertically, *but not diagonally.* Have I missed something?

[@CharlieGaduber]

To start off with, intuitive thinking shuld be used at the outset. Schrodingers cat was a stray named "bunch" and she was a girl cat with a taste for drama. "bunch" owned several masks to prevent bad breath." Bunch" never shared in the Nobel prise.

[@ThePianistOS]

The analogous measurement to performing your 45° rotation is a Hadamard gate. Suppose you have decayed (ground) and not decayed (excited) in the un-normalised superposition |g> + |e> Then you can apply a pi/2 pulse which has the effect of rotating back the state to |e> which can then be detected. In this way, you could test that a given ensemble of states are in the superposition |g> + |e> by performing the pi/2 pulse and measuring to see if the atom is excited with P( |e>) = 1.

[@thefreshest2379]

How much decoherence is in the system? is a very important factor. Especially when talking about observers.

[@pmetham]

But are the "filters" actually filtering? What if, in fact, they are absorbing the incident light and retransmitting it with an orientation that is determined by the filters structure. In the case of a 45 degree filter one now simply has a new light source angled at 45 degrees to the original orientation - really much the same as you started with, albeit with some loss. There's no reason why you should not be able to repeat this operation with a reasonable expectation of still obtaining substantial overall transmission.

[@TedToal_TedToal]

I just love your videos and the way you think and the way you approach this. I need to keep hearing more until someday maybe I will accept or understand quantum mechanics. I don't know.

[@TimothyJohnLukeSmithPSA]

Have you considered using colored filters, like photographic gels, to demonstrate color states? For example, a blue gel will block the orange spectrum, while an orange filter will block the blue spectrum. Would that be a more visible method of the state such as an alive or dead cat?

[@erikayer2146]

If the cat meows from within the box and you hear it, does the cat self-collapse its own state?

[@michaelbourrell2693]

We're still not sure about the cat.

[@glynnevans4531]

There are not two states if the cat has been in the box an hour say. State 1 cat alive, state 2 cat dead for 59 minutes, state 3 cat dead for 58 minutes etc. Open the box - autopsy tells you how long it's been dead. Completely different from spin up or spin down. If spin up you cannot detect at what time it started being up. That's the difference. The cat could die at any time and so the state of decomposition tells you how long it has been dead. Unless it died in the last second you know there is a period during which if you had "measured" you know what the result would have been. Ergo There is no superposition at any time.

[@Roy_Godiksen]

13:00 What would happen if you had another filter behind the one in your hand. there should technically not be any light, as you have blocked both vertical and horizontal. But if 100% passes through the vertical, would it also then pass the vertical if you placed the filter 2 cm behind it?

[@sebastiandierks7919]

A major misunderstanding with Schrödinger's cat I think is that it is presented without clarifying that we assume perfect isolation from the surroundings, like air molecules, the cosmic microwave background, atomic interactions within the cat itself etc. If all components of the experiment are perfectly entangeled without any surrounding interactions, the atom, the detector, the poisonous gas container, the cat, and even the experimentalist would all be entangled and in superposition. If then any component of the system is undergoing a measuring interaction, like the atom getting hit by the cosmic microwave background, or the experimentor opening the box (so that light from the room can interact with the cat), the superposition collapses and the cat is either dead or alive. But of course, if you did that experiment in real life, the detector, the gas container, the cat and the experimentor are measured all the time, through interactions with the environment and through interactions within themselves, being macroscopic objects. Or have you ever been in a quantum superposition just because you are in the same room as a banana containing a radioactive potassium atom? So if you did that experiment in real life, it is in fact like the un-opened letter, there is a classical probability representing your lack of knowledge for the cat being dead or alive, and not a quantum mechanical probability representing the uncollapsed wave function, because it is collapsed all the time by interactions with the environment, thus decohering the system towards classical probabilities. It's just not the point of the Gedankenexperiment, which indeed does take place under perfect conditions without interactions with the environment, where the superposition and entanglement of the components stays intact over long periods of time. So in the Gedankenexperiment, the cat is both dead and alive at the same time, while in real life, it is not.

[@amihartz]

I think the most thing people get wrong is that they say the cat is in a superposition of alive and dead, such as |alive> + |dead>, and thus could exhibit interference effects, but this is factually wrong. The cat would be entangled with the detector which would be entangled with the particle, so you would have to assign the wave function to the whole system, not the cat individually. Indeed, if you want the cat individually, you would need to do a partial trace to get the reduced density matrix for the cat, and in doing so, you would have a classical probability distribution, so you would actually not expect the cat on its own to be capable of exhibiting interference effects. Another common misunderstanding is that the point about the experiment is to demonstrate that cats can be both simulateously alive and dead, when Schrodinger actually presented the thought experiment as a reduction to absurdity. He believed it was so ridiculous to believe cats can be both alive and dead simulateously that nobody would buy it, and because it is a logical consequence of believing particles can be in many states at once, he was explicitly making the argument that we should reject that particles can be in multiple states at once. Schrodinger's later writings took on a position rather similar to relational quantum mechanics. He argued that we should abandon continuous evolution entirely and treat particles as only existing in the moment of interaction, and the wave function is merely a statistical tool to predict how it will manifest in the interaction, and does not describe a real entity. The photon in the double-slit experiment, from Schrodinger's perspective, does not "spread out" into a wave and then "collapse" back into a particle. Between the laser and the detector, the photon is not meaningfully anywhere at all and has no properties, since it only exists during the moment of interaction.

[@TimoBlacks]

​@@amihartz "He argued that we should... treat particles as only existing in the moment of interaction, and the wave function is merely a statistical tool to predict how it will manifest in the interaction, and does not describe a real entity." That one should not craft up physical entities as some kind of poetic drunken response to staring at a bit of helpful mathematics, was obvious since before QM. The fact that he needed to say that, and that people such as yourself need to repeat or emphasise him 100 years later, means the world is but destined to be drunk. While I appreciate your attempt to clarify, and I agree that you did so correctly, I think it is trivial to spend time with correcting or even dealing with drunks; better to spend time in making sense of physical phenomena. Such as that at the microscopic world. You know, doing physics. There is nothing to understand per physics, except what Nature shows us as physical phenomena. No measurement problem is shown. No collapse is. No signal from one particle to another is. Etc etc. The task is to describe and explain Nature's phenomena, not made up phenomena. Since before QM. If one keeps that in mind, one avoids all that is a mistake. Let the rest drink up.

[@carlhitchon1009]

@@TimoBlacks QM does not really explain what's going on. It just has math that can predict, statistically, what things happen and with what probability. It does not explain how an electron in the two slit experiment, behaves exactly like a wave (statistically) but the energy, mass, and charge associated with the electron magically appears in some tiny spot on the screen when it interacts.

[@TimoBlacks]

​@@carlhitchon1009 What do you mean "does not really"? We use QM for nothing except making predictions. That means QM does not AT ALL explain what's going on. It's not its business, or interest, to explain. Just as the tensor mathematics in GR does not explain gravity. Not "does not really" but does not AT ALL. An apple does not walk a dog (not, "it does not really walk a dog", as if it _sort of_ did). Also, incorrect to say that a single electron acts like a wave statistically. A single electron does Nothing statistical. When we talk statistics, we're talking SUMS, and it is those sums (statistics) which (for reasons we do not know) bare a correspondence with wave amplitude (though we must square it). And there is no "magical" appearance of an electron. What is causing you to think that it is "magical" is that you cannot help but think "classical". That is, you are thinking as if no electron can show up at any place unless it _travelled_ to that place. But Nature has (for 100 years) been showing us that such way of thinking is incorrect. That way of thinking --- is wrong. Since that way of thinking is wrong, there is no magic. There is only the difficult task of getting to know the correct way of thinking.

[@HoD999x]

Question about 13:00 - why don't we say the filter repolarizes the light?

[@philo5923]

Thank you so much for this great video. As a physics aficionado, it always excites me to watch them especially because it incites me to learn more.

[@LeonardoBartoloni]

The definition of measurement is usually based on whether the object doing the measurement is internal or external to the isolated system. If you include the thing doing the measurement in your system it becomes entanglement between the thing being measured and the thing measuring it. That's what happens to the cat and the killing machine. The cat's life becomes entangled with the radioactive atom's state, and measuring one or the other will make the other collapse as well.

[@kreynolds1123]

Not only is the cat in a superposition of being dead and alive, and the wave function collapses on opening the box. But there are different posssible dead states where the cat could have died any time between when you closed up the box to the point where it died moments before you opened the box.

[@amihartz]

To clarify, if by superposition of alive and dead you mean |alive> + |dead>, then this is factually wrong and simply not quantum mechanics. The grammar of quantum mechanics simply disallows complex systems to be in a simple state like this. Every time a particle interacts with another in a way where the altered state of the latter can be derived from the state of the former, they are going to become entangled, and when they are entangled, then you cannot describe them individually. You have to assign the wave function to the entire system. The detector would thus become entangled with the emitted particle, and then the cat would become entangled with the detector. The "more correct" (although still a simplification) representation would be |notemitted+notdetected+alive> + |emitted+detected+dead>. This difference actually does matter because if you want to know the state of the cat on its own, you have to do what is called a partial trace to get the cat's reduced density matrix, and doing so will you will find that all the coherence terms for the cat reduce to zero. In other words, the cat would not be capable of exhibiting interference effects on its own. If you isolated the cat from the other parts of the experiment, the cat's state on its own would still be random, but it would behave classically, i.e. it would follow a classical probability distribution. Only the entire system as a whole could exhibit quantum interference effects. You can see this with something like Bell tests. You can conduct a Bell test by first entangling two particles by having them interact whereby one effectively "records" the state of the other, kind of like a measuring device. If you then immediately isolated the two particles, they would behave classically in the immediate subsequent interactions. You could only observe interference effects of the two particles taken together, as a combined system, which shows up in violations of Bell inequalities. However, it is impossible to view these violations of Bell inequalities separately. You have to bring the particles back together to observe them. They are properties of the combined system and not of their individual parts. The individual parts actually follow a classical probability distribution in isolation. This is why, for example, photons stop being able to form an interference pattern when you measure the path they take. Your measuring device becomes entangled with the photon, and thus interference effects could only be observed in the combined system of the photon and your measuring device taken together. Yet, only the photon on its own, in isolation, passes through the two slits, and thus the photon follows a classical probability distribution rather than a quantum probability distribution (i.e. those where the density matrix has non-zero values in the coherence terms aka the off-diagonals).

[@kreynolds1123]

@amihartz I'm speaking of a cat (not really) in a larger complex quantum system that can be described by more than being in one of two states. In the case of a cat, we might be able to determin how long the cat has been dead after the box was opened. Or instead of a poison to be delivered to and kill a cat, we could have rigged a timer to an unstable isotopic trigger. After 1/2 life there's a 50/50 chance that the timer was triggered. Would you care to calculate what is the most likely reading on the timer?

[@amihartz]

@@kreynolds1123 My point is merely to clarify that in this "large complex system" that can be in one or two states where the cat is just part of it, then the cat taken in isolation cannot exhibit interference effects and it would be factually wrong to describe it in terms of something like |alive> + |dead>. I am just clarifying this for any potential readers because many people misunderstand this. I have seen plenty of videos on KZbin that even write out "|alive> + |dead>" in the video, when this violates the basic rules of quantum mechanics.

[@TheIvalen]

Sort of get it - but you keep premising the 45 degree magic with "we start with all horizontal light because of the filter". Obviously it's not all horizontal light. A filter doesn't just magically make 45 degree light simply because we're measuring it that way. So the light wasn't all horiz to begin with.

[@FunFindsYT]

It only lets through light at a certain angle, so you know which angle the light is after passing the filter, because the other light does not pass through

[@cmfortblynumb]

The photons are practically random when they exit the pointer, and then the filter doesn't let the ones which are not horizontal go through, so all the light after the filter is horizontal (the rest gets absorbed by the filter).

[@mrnobodyspecial]

Alice, both of the polarized strips were oriented in the same direction, at 45° (in the video at 12:58) so the nuance of being at 45° is moot. You failed to follow up the measurement with at least three additional measurements at 0°, 90° and 135°. In those measurements you would get a 50% reduction at 0° and 90° and 100% at 135°. You do somewhat cover this in 24min-29min in the mathematical explanation Keep up the good work with these videos. Your first video explaining the double slit experiment was the first good explanation I had ever heard on the “why”, and I have always been about the why. 🤩

[@tygertyger8597]

That ring on your finger just collapsed the superposition of all my hopes.😟☺

[@MechMon]

13:06 - I don't see how a photon knows which way is up. If the first film aligns the photons in "a direction" and you align a second film in the same direction, I would not expect there to be blocking going on. In the single hair splitting experiment it was shown that a single hair splitting the beam shows the wave nature of the photons. Okay I saw it, I believe it! But a hair is pretty large and the interference pattern was measurable. So how does that compare to the "thickness" of a single polarizer line? I would imagine a 90deg rotated film would just destructively interfere. Second question, assuming the polarizer lines are of thickness "T" with a spacing "S" and they are equal, what happens when the second film that is aligned with the first is offset a distance "T" orthogonally to the alignment direction?

[@IvanToman]

At 13:10 both of your polarizers are in the same direction, right? I mean, both are at 45 degrees? It is completely the same setup as if both are vertical or both are horizontal or both are at 10 or 60 or whatever degree... the important thing is that both are in the same direction, then of course no drop in light will be seen. Why we even need quantum physics to expect that? Isn't that obvious? Whatever light goes through first one, will go through the second one, too, as it has the same direction.

[@kpunkt.klaviermusik]

What I do not understand: what difference does it make if an "observer" is looking / measuring or if there is no observer and the outcome will be different. And how do we know that the outcome is different?

[@wmstuckey]

You nailed it, Mithuna. As with my Comment on your video “What is Spin?” let me give the corresponding explanation of Schrödinger’s Cat per quantum information theory. Accordingly, I need to start with an important distinction between a classical bit of information (like a computer bit being on or off) and a quantum bit of information (a qubit). Both bits produce one of two outcomes when queried (measured), but a classical bit has only one measurement possible while a qubit can be measured in many different ways (infinitely many, actually), each with two possible outcomes. In Mithuna’s polarizer qubit, the polarizer is rotated through 360 deg and always produces one of two outcomes - photon passes or photon does not pass. For the qubit of the Stern-Gerlach (SG) experiment, the SG magnets are rotated 360 deg and always produce one of two outcomes - electron is deflected towards the North magnet pole (“down” or “-” per Mithuna’s convention in her video “What is Spin?”) or the South magnetic pole (“up” or “+”). Consider electron spin, as in Mithuna’s video “What is Spin?” As I explained in my Comment there, the horizontal spin measurement of the vertical up spin state |V+> produces each of its two left-right, |H+> and |H->, results in 50-50 fashion. This is exactly what you hear people say about Schrödinger’s Cat, i.e., you open the box and find the cat is dead with 50% probability or find the cat is alive with 50% probability. With that information alone, Schrödinger’s Cat could be a classical bit or a qubit. If Schrödinger’s Cat is a qubit, then there must be a measurement of the cat-box system like the vertical spin measurement of the state |V+> that produces |V+>, i.e., |H+> + |H->, with 100% certainty. [This is the counterpart to the measurement Mithuna did with her polarizer at 45 deg, showing that |45 deg> = |V> + |H>.] We know the measurement “open the box” producing “Live Cat”-“Dead Cat” results in 50-50 fashion is analogous to the horizontal spin measurement of |V+>, so what is the measurement of the cat-box system corresponding to |Live Cat> + |Dead Cat> with 100% certainty in analogy with the vertical spin measurement of the state |V+> that produces |V+> with 100% certainty? And what does its outcome mean physically? If you can’t articulate that measurement and outcome of the cat-box system (as Mithuna admitted), and every possible measurement between that measurement and the “open the box” measurement, then the cat-box system is just a classical bit ... like opening a box to find a ball or no ball. No quantum superposition there 🙂 To read more about the quantum information approach to the mysteries of quantum mechanics for the “general reader,” see “Einstein's Entanglement: Bell Inequalities, Relativity, and the Qubit” (Oxford UP, 2024).

[@Hecatonicosachoron]

How did you resist the temptation putting the filter at 45 degrees between the other two? It's a neat demo

[@ghefley]

It is because of communicators, like you and others, that I am able to peek and then comprehend fathoms of layers of beautiful-mind works and patterns that are far too subtle for my level to approach without shattering; but to glimpse … just a glitter was enough to make my level no longer far enough.

[@joepike1972]

7:25 Or it is light at 45 degrees and filters passed at 45 degree to it cut out about have of that one light. I am not accepting this idea of it being a different or super positioned light. Of that the perpendicular light is the other half of the light. It is like a stream of water in a river. Just because I put barrier at certain angles does not mean the water is compose of two different "waters" and that different angled barriers got half of the water or the exact other half of the water. I see it as still only have of the water flow and not fundamentally different water from different filters.

[@joepike1972]

17:36 with the atom I am pretty sure the atomic weight of that atom is going to loose it super position at the exact moment it decays. If it decays, materially it is going to be atomically different. The energy coming from it can be in a super position, but this the random possibility happened to the material system, that material system will be its own form of measurement that will collapse the super position.

[@donsailing3366]

Question on Quantum entanglement of photons. How do we know that half the photons were not absorbed by the first filter and those photons that passed through rotated by 45 degrees? It seems that would create the observed effects.

[@carpcarpbread]

But like, the university letter probably was in a superposition for less than 10^-60 seconds before decohering with the environment...

[@chainbenwa2713]

Whoa slick! You upped your laser game with the filters! That was kewl

[@poogitypooheh]

Is superposition a third state that sits between the two states, like the 45 degree interpretation? Or is it better to think of it as both states at once? Is there a difference?

[@joepike1972]

4:23 I am sorry but once that radioactive decay hits the detector to release the deadly gas, is that not the "measure" that collapses the super position?

[@TimoBlacks]

Yes it IS the measurement. Meaning, there IS a fact as to whether the cat is dead or alive. Basically what you are showing is that this situation of cat in superposition would NOT actually happen. Which brings us to the point: The goal (of S) was not to make you think it WOULD actually happen. S only wanted to bring the quantum issue up to the scale of something more relatable (like a cat, nice and big), so that it makes more clear and easy for everyone to see how crazy this quantum world is. No different than, say, you explaining gravity in a non perfect way so that a young person can get the concept. Eg, you might during your explanation use the word "pull" somewhere (when actually in gravity there is no pull). Then the kid says NO! HOW CAN THERE BE A PULL! Then you have to tell them "Don't take it literally, just look at the overall idea". Well, that is what S would say to you.

[@MatthewSuffidy]

It is an upscaled quantum sensor scenario. What I say is if you have a sceientist around cats are more probably dead. I see the polarization more like this: You have light coming out in any polarization that is not just up ro down. You are using a first polarizer in a certain arbitrary way. That means the output is mostly polarized. So when you have a second polarizer. It mostly works when it is the same way as the first one and outputs less going past 45% of the fist one. That is because almost all the light is polarized in the opposite way but some were on the edge.

[@protocol6]

This always seemed like a misunderstanding of the nature of polarizers to me. You can do the math for a polarizer as a probabilistic rotation of a continuous orientation toward a specific orientation. So light is absorbed or rotated probabilistically. Then the light that passed through a polarizer is mostly oriented in the direction of the polarizer and some will still pass through another oriented at 45 degrees, getting rotated again. The odds of it being rotated enough to pass through decrease to nothing the closer the photon's initial orientation is to 90 degrees from the filter orientation. This solves the "inexplicable" 3-layer version where you have two filters at 90 degrees that block all light and then it "miraculously" transmits some light when you insert a third filter in the middle at 45 degrees. The math for this is nothing new but I've worked it out before in a spreadsheet and was able to get the intensities seen in the various experiments.

[@joepike1972]

16:35 Sorry that just came off sounding so hand wavy. Not that I don't understand how it was an effective counter to the whole particle idea. But more that it makes no sense to not think light filtered at 45 degrees with be completely unblock by going through a filter polarized at the same angle. It is like you set up a story that doesn't apply, prove it doesn't apply and then try to act surprised by a completely sensible result by trying to interpret it as something that we have no reason to imagine be the situation, the idea of component vectors being something in the real field verses how we are thinking about the measure. The fact that should give us a clue something is off my looking at things that way is that we become surprised by what is otherwise a completely unremarkable result, a filter in paralel to a polarized filter will let the same form of polarized light through.

[@joepike1972]

8:03 that would be even further from my interpretation. My interpretation is all of it is the same form and you are just halfing the same form from both filtering method. That there is not some kind of fundamental different that this particle model is further leaning into.

[@user-xf6ig9ur2y]

I wonder if a lot of this could simply be explained by imperfect filters. I.e. perhaps the filter is only as good as the cosine of the angle squared - letting all 0 deg polarized light through at cos(0) * cos(0) = 1, letting 50% of 45 deg polarized light through at cos(45) * cos(45) = 0.5 and letting 0% of 90 deg polarized light through at cos(90) * cos(90) = 0. Do we know that the filters are nearly perfect and how do we know that? Or are they imperfect as per my hypothesis?

[@schmetterling4477]

The filters are simply NOT acting on a scalar space state. The correct description of a filter is a linear operator acting on the linear combination of two polarization vectors. A linear operator acting on a vector is a matrix. It has more than just one component. In this case it has four and energy conservation restricts those coefficients, but you still end up with an operator that describes both, an extinction coefficient AND a vector rotation. We demonstrate all of this in first semester experimental physics with a column of glucose solution. Every person who has ever grown wine knows how to measure the sugar concentration in grapes with a hand held refractometer. Are ANY of you paying ANY attention in the experimental physics classroom???? I don't think so. The amount of total delusion about reality is staggering.

[@user-xf6ig9ur2y]

@@schmetterling4477 Thanks for the reply. I want to re-reply with 3 points: 1. I was struggling with the filter in particular and I think I resolved the issue. You're reply has also shed some interesting light on the subject. I finally concluded that the filter is passing the component of the light polarization vector in the direction of the measuring filter and blocking the component in the perpendicular direction. Seems simple enough and looking back I'm now saying duh - but I was hung up on that. Or is that incorrect! 2. If a filter is PERFECT then it would seem that no light would pass through it. I'm looking at this as a probability distribution (PD). In a PD the probability of a discrete outcome (a perfect measurement/filter) is 0. To get a non-0 probability (some light) you need to consider a range (an imperfect filter) of outcomes/events. I'm assuming the polarization of the light from the laser is random here. 3. I'd like to suggest that you back up and do a basic video on the measurement filter issues. When I was watching the videos I continually had questions regarding the filters and what they're doing and that kind of distracted from all the points being made. This is especially the case since the experiments are all based on lasers and light and filters, Anyway, these videos are certainly making me ruminate and I guess that's what they're intended to do! Thanks, D2

[@schmetterling4477]

@@user-xf6ig9ur2y Congrats, you just reiterated that you not only are not listening in the classroom but that you also prefer to distribute the mental debris of your failure to pay attention instead of correcting yourself. Yes, that such a filter simply selects a certain polarization is 100% incorrect and we are teaching all of this in first year physics. All you guys have to do is to LISTEN to the teacher instead of your own inner voices. Your inner voices know nothing about physics. The teacher usually does. :-)

[@zlac]

I realized what's going on when I started counting the Geiger counter as an observer. However, in all probability - the atom that decays is "the observer" itself, so the decay is observed way before the Geiger counter detects the decay. Uranium atom is not a photon. It's not traveling around in vacuum or wherever so "nobody knows" With radioactive decay, we have the whole atom, and atom has many particles and they're all affected by the decay, they "know".

[@amihartz]

The reduction of the state vector is merely an update of a probability distribution based on new information acquired, so it is something that occurs relative to the information accessible from a particular frame of reference and does not represent the occurrence of a physical event (as if a physical wavy thing out there floating in Hilbert space literally "collapses"). The reduction of the state vector is thus relative to a chosen coordinate system. Anything can be an "observer" even a single particle. You pick a coordinate system centered on a particular object, and that is your reference frame, and the wave function you write down can look different from different reference frames, including when the "collapse" occurs.

[@rogerjohnson2562]

The filters experiments show that some of the light is reoriented as it passes through slits; it doesn't prove uncertainty of the waveform...

[@retiche]

Explaining wave collapse with a cat is a little bit off, because you start from a certain state of cat (alive, and this state depends on the entropy of the system). Thus the superposition is more toward the cat being alive than dead. Anyway, there are some other considerations: the state depends on time (entropy of the atom) - it's like a flipping coin, you don't know where what is it until the moment you catch it. If you catch it sooner or later you could have a totally different result. But since the cat is alive, you can test the atom superposition until the cat dies, but not in reverse. And this way we get back to arrow of time. I don't believe quantum is the way to go. We didn't see any major breakthrough in physics in the last 50 years or perhaps more.

[@CeeJMantis]

There's been a lot of technology that have been invented that rely on quantum mechanical effects. What do you propose as an alternative that still explains the measurable effects of quantum mechanics, but doesn't rely on the current explanations and interpretations?

[@retiche]

@@CeeJMantis I do not contest the validity of the quantum field :) Quite the contrary! Even though, the way the science works, is that we don't really understand the phenomenon, if we get the rules of how it works. So it is possible, that what we understand now could be tomorrow something else. Anyway, what I tried to say with the cat is that some of the thought experiments aren't really matching the reality and that quantum field has achieved more or less it's peak, there are not too many things that could lead to physics progress, as there are also not too many from the string theory, even though there are people that work non-stop on the field, wtihout any results. We keep redoing same experiements and inventing other ways to look at it, like the quantum delayed choice, that lead us again and again to the same conclusions. Still, we keep testing, despite the results.

[@retiche]

@@CeeJMantis what if I tell you that I think there is something else that could explain more? of course, not relying on spirits, or some hidden variable, but based on good old vectors? Also, of course I'm not a carrier physicist, and I don't really know everything that might need an explanation, so I could be very well wrong :D

[@CeeJMantis]

@@retiche I'm sorry. I misunderstood what you were saying. It may be that many things in the world of theoretical physics are approaching a point where testing them experimentally is simply unfeasible because the numbers required are either far too big or far too small to measure or detect. However, there's still value in retracing old ground, and I suppose one could argue that a lack of breakthroughs demonstrates a thorough, if unintuitive, understanding of the world around us.

[@williambunting803]

It is wrong to say that the “light” has a super position. Superposition is determined at the individual photon level not the “flow” of photon level. The light beam is a mixture of photons which are blocked differently depending on their polar orientation. I believe. The best example of a photon with a superposition would be a Neutrino which must be a multi phase non harmonic electro magnetic photon which cannot be absorbed due to rarely being in phase with matter particles. With the 45 degree light passing through is most likely to be a property of the filters rather than the light. The thing with anything quantum being observed is that observation requires energy being absorbed which inevitably changes the state of the quantum system.

[@schmetterling4477]

Photons are not in superposition. Only an abstract mathematical quantity that describes the lack of our knowledge about the next detected photon is. But that quantity is an abstract. Nature does not know anything about it.

[@prajwalms_001]

Other than this example, can we say that light is superpositioned between being a particle and wave? Because unless we measure light, we can't say which state was it in right? I'm not saying this is right, I have a doubt.

[@MiteshJethawa]

Light is A Quantum Objects Which has Particle Properties and Wave Properties, They follow Their own rules they're not Particle , Waves or A Superposition of Them , for ex Metalloids Have Some Properties like Metals And Some Properties like non-metals but we don't say they're are mixture of Metal And Non-Metals , . (about your we can't say which state is in when we definitely can) Light is Not a Superposition because if it was a Superposition It was 50% Chance It would act as Particle And 50% Chance to Act as Wave during any Experiment but during photoelectric effect it always acts as Particle and During double Slit experiment it always acts as Wave (we can definitely say during the photoelectric effect light will always acts as particle 100% no uncertainty)

[@allthekidsareright]

13 min in…I don’t understand why that was surprising. When it was aligned vertical and you put the filter vertical 100% of the light went through. The same held true at 45 degrees. Am I missing something there?

[@davidaugustyn9234]

did you take any chemistry classes

[@britgorlicki2533]

I read Rovelli's Heligoland and picked up something that really made me feel like I grasped this a little better. I am a layman and in no way formally educated in this stuff so set me straight if you need. In the book it described quantum states in systems, up to large ones. So in the cat/box example, if the atom decays and the machine detects it then the position has collapsed *relative to the machine* but not necessarily relative to the soon-to-be human observer. That the machine is now also in a superposition of colapsed and not colapsed relative to that person. And only once the human "enters" that system by observing it does the whole thing become "real" or "colapsed" or "certain" relative to that person, but that person is still in a superposition relative to some alien somewhere outside our observable universe. This lends to why these experiments must be so isolated, to create a small system that is not being affected by its environment. You just put a cat in a cardboard box and this wont happen cause the cat is interacting with the box and the box is intracting with the table and the table is interacting with the floor and you're standing on it. This creates a whole web of systems super tiny and super huge of relative "realness" from the perspective of any person or rock or star. This explaination really clicked with me, although I don't know if it's correct.

[@schmetterling4477]

The problem is simply an inconsistent use of "closed and isolated system". One can not peep inside a closed box without changing its inside. Schroedinger didn't understand this triviality. He wanted to have his cake and eat it, too. This whole collapse business is just intellectual nonsense. Well written quantum mechanics textbooks like Sakurai don't even mention this term. It's useless and distracting from the proper analysis.

[@amihartz]

@@schmetterling4477 I see you comment everywhere, you never do any research and have no background on this subject at all and simply go around throwing personal attacks at everyone, which I know for a fact you will just reply to my comment with a substanceless personal attack, so I am only replying for other potential readers, not for you. If you actually bothered to read Schrodinger and not make things up, Schrodinger also came to reject "collapse." Schrodinger in his later writings agreed that it makes no sense that measuring devices should play a role and that some smeared out particle "collapses" into a definite state due to measurement. He instead argued in favor of something fairly similar to what would later become relational quantum mechanics: the particle only exists relative to what it is interacting with in the moment and has no independent existence, and the wave function is merely a helpful statistical tool to predict where it will show up in the next interaction. If you ask the "history" of how it got there _in between_ the two interactions, then what Schrodinger argued is that you will always find that there are "gaps" in this history that are impossible to fill, because the history ultimately doesn't exist. The particle isn't anywhere or doing anything in between interactions, it only exists in the moment of interaction. It never spreads out into a wave, and so it also never collapses back into a particle. It is always just a particle hopping between interactions.

[@amihartz]

Yes. I would recommend you check out the contextual realist interpretation, it's probably the simplest I am aware of. It is very similar to relational quantum mechanics and avoids the majority of the "weirdness" of quantum mechanics with a simple principle: what is ontologically real is precisely what we observe it to be. What is real is not the mathematical description of something. The mathematical model is a map we use to predict what we will observe. But the territory, what is real, is what we are immersed in every day, what surrounds you, what you actually observe in experiments. If you take this approach, then what is real necessarily can only exist in the moment of interaction, and is relative to a chosen reference frame. For example, if I observe a ball, this is only possible if the ball is interacting with me in some way, and I describe myself as the "observer" because I am describing the ball from my reference frame. If I cannot observe the ball, then it is not interacting with me. It may be interacting with someone else, in their frame of reference, and thus it would be real for them, but not for me. Indeed, we can both look at the same ball, but because we perceive it at different angles, we would perceive something different. What is ontologically real depends upon context. Context is just whenever two things interact, you have to choose one of those objects as the basis of your coordinate system, a frame of reference, in which to describe the result of the interaction with the other object from. Whatever is chosen as the basis of your coordinate system gives you the context under which all other things can be described. Since reality is contextual, there also is no "absolute" godlike perspective that can see everything simulateously. Reality only exists in terms of contextual descriptions, and thus it is invalid to simulateously juxtapose different context frames. If you take this idea seriously, then you can explain the whole Schrodinger's cat thought experiment without introducing the notion that the cat is both alive and dead simulateously. From the cat's context frame, it is either one or the other. From the person's context frame, if they have not yet opened, and thus interacted, with the box, then by definition the physical event has not yet occurred, and so it does not even make sense to ask the ontological state of the cat from their context state. It has no ontological state. Again, if you choose the human observer as the basis of your context frame, they have to physically interact with the box an ontologically real event to actually occur, which is precisely equivalent to what that person would observe. So if they have not interacted with the box, then this physical event did not occur, so it does not have a value because it factually hasn't even happened. When they do open the box, however, from their context frame, they will again observe the cat only being in one state and not another. The ontological state of the cat from their context frame thus also would become a cat that is in one state and not both simulateously. At no point for either of them do they exist in a superimposed state. When you write down a wave function for a system, you are thus not actually describing the system. It is instead a statistical tool to predict what the system's properties will be in the future if you were to interact with it. Imagine if a person takes medication with a 50% effectiveness after 1 year, but 1 year hasn't passed yet. It's not as if the person becomes smeared out in a 50%/50% probability distribution of cured and sick simulateously. No, the 50%/50% distribution just simply even isn't applicable yet. It describes a real physical event that has yet to actually occur: the results of the medication after 1 year. It is only valid after a year has passed. It is not a description of the right now person, but a prediction for a future event that has yet to happen. Similarly, the wave function is used to predict future events, when a but does not actually describe the system. The ontological state of the system, from your context frame, is precisely what you observe it to be, which requires you to interact with the system. From this approach, not only do particles no longer literally "spread out" like waves that "collapse" upon measurement, but you also get rid of the supposed "spooky action at a distance" as well. Rovelli explains why very well in his paper "Relational EPR". You entirely get rid of the need to talk about "measurements" as if they play some fundamental role as well. You don't need to posit anything grand like a multiverse. The supposed "retrocausality" allegedly shown in some experiments like the delayed choice experiment also disappear.

[@schmetterling4477]

@@amihartz My background? I am an experimental high energy physicist. Unlike Schroedinger I have literally made trillions of quantum measurements and I have designed and built parts of one of the world's largest high energy physics detectors. I read Schroedinger's very confused polemic against Copenhagen. It's complete intellectual nonsense. He simply didn't understand the behavior of nature. That quantum mechanics is simply a non-commutative solution to Kolmogorov's axioms was known to von Neumann in 1932 (that's one year BEFORE Kolmogorov published his axioms for probability theory and which happen to have much broader implications than he thought). von Neumann had figured all of this out three years before Schroedinger even coined that unfortunate (and completely misunderstood) cat in a box example. Of course the outcome of an experiment depends on the measurement system. That's the entire gist of quantum mechanics (as compared to classical mechanics). What do you think the Born rule is? It's the mathematical description of the system behavior of the measurement system. Can you do without it? Absolutely. You do quantum field theory and then the only and ultimate energy sink is the physical vacuum at infinity, i.e. all physical states automatically become plane waves that get scattered at an interaction point. That's the modern view and it cuts through all this bullshit. A glimpse of that can also be found in von Neumann's book, in chapter six, if I remember correctly. You should really read it. Once you do you will find that Schroedinger, Einstein and even the older Heisenberg were basically struggling to keep up with von Neumann and Dirac by that time. Heisenberg is still worth reading because his matrix mechanics papers contain the correct ontology of the quantum mechanical process. Copenhagen is well worth analyzing because it has the correct mapping from physical reality to theory. Born, in particular, is worth thinking about DEEPLY. Schroedinger, EPR and a slew of other nonsense was just muddying the waters of a beautifully simple theory that is, at the end of the day, nothing else than a relativistic partition of unity. But you knew that, right? If you didn't, then you have a lot to learn because you can't even keep up with an aging experimental physicist right now. ;-)

[@schmetterling4477]

@@amihartz Wow, that was a very long winded way of telling us that you weren't paying any attention in school. ;-)

[@HJRC_]

What is the name of the light filter being used here?

[@MarkRawling]

The light coming out of the laser is already collapsed by your filter. You don't appear to have explained how/if such light can then be used to explain subsequent quantum effects - when does it become "uncollapsed" for the purpose of proving superposition? Just by choosing a different basis? Eg, here, of course you measure 100% at 45 degrees, there's no apparent need to invoke superposition to explain that.

[@peetiegonzalez1845]

If you make it all the way to Elitzur-Vaidman interaction-free measurements and the implications of Wheeler's delayed choice experiments with this clarity I think I'm going to have to bookmark the series and have it on speed-dial to send my friends any time a discussion of quantum mechanics comes up.

[@_-Skeptic-_]

how something, like your light, having two components or vectors (vertical and horizontal) can be compared to super position?

[@SuperpositionSimon-vt7cc]

Nice Video, but the explanation at about 20:00 doesn't prove, that a measurement is made without a conciouness observer. If you put another filter at the end and watch the result, it's just the same as opening the box and only watch if the cat is dad or alive. If the cat is dead, the atom must have been decayed, because it is entangled with the cat. So here if you put another filter at the end and watch the result. The last filter is entangled with the previous one and so you can't rule out that the light has no defined value until observing it with a conciouness at the last filter. Actually I'm really interested why most physicist rule out, that a conciouness observer is not neccesary for a measurment. So if I got your explanation wrong, please tell what exactly proves, that a measurment is independend of a conciouness observer.

[@peetiegonzalez1845]

Penrose has described experiments to gradually increase the size of the system that must be in a state of superposition, and see how large a system can still show measurable effects.

[@KaiseruSoze]

How do you predict outcomes in QM? Statistical mechanics. It's lossy and we don't know what we don't know so we can't say how much information is lost. And we are switching from a statistical context to a deterministic one. It's like doing a calculation with oranges and predicting apple outcomes.

[@sinisterai]

the light is already in a superposition with the waves starting from a visible origin, pointing in one (polarized) state but also being invisible while transiting the open space (also filled with non-experiment related light) until it is intercepted (or observed) by the destination surface where it becomes visible again. Many things are in more than one state (superposition) even if witnessed by only one observer. (and there never was a cat and its name was Pierre Laplace.)

[@JrgenMonkerud-go5lg]

btw in my long winded explaination of how collapse works in a model where light is basically classical as it travels, the light doesnt collapse when interacting with photomultipliers, only when it interacts with atoms or other systems that absorb chunks, well it still can, but only when it does that, when it only displaces chargest elastically in the polerizer to cause transmission or reflection it doesnt do that, it just keeps going like it was classical, there is a pretty sharp divide between elastic and inelastic interactions of light and matter in this sort of picture. so in an idealization of a completely elastic polerizer, which can be simulated as i said by selecting outcomes with 2 measured photons in a 2 photon experiment for example, then you end up with light propagating and being transmitted only in the polerization corresponding with the polerizer, and only when it is inelastically absorbed by a bound state like an atom or photo multiplier does a collapse occour across the wavefront, and the result is that we can get completely classical accounts of all of the phenomena of light, including entangled light.

[@vanikaghajanyan7760]

22:11 In fact, the observer's self-esteem in QM is underestimated to the level of the infamous ostrich. 0.The observer is always involved in an unavoidable measurement process. 1.It seems that there have never been any problems with QM already within the framework of GR (for example, in the case of the Schrodinger/Carroll cat). 2.A live cat breathes and, accordingly, emits gravitational waves according to the formula GR with intensity: I(G)=(2G/45c^5)(M^2)(l^4)(w^6), where M is the mass of the cat, l is its characteristic size, w is its frequency breathing. 3.The frequency of gravitational radiation should be on the order of w~ 2π/т where т is the characteristic time of accelerated mass movement (pulsation, rotation, collision, non-spherical explosion). 4.It is clear that the dead cat is not breathing and I(G) =0*. 5.In principle, all this lends itself to a certain (improbability) constant measurement without opening the "black box", since gravity is not shielded [w=w(m)]. Moreover, the behavior of the radiation source is also controlled, since it emits only in an excited state. ** 6.Of course, Carroll's sleeping cat breathes, but differently (can be measured) than the waking one.*** 7.Sweet dreams to you QM, on the interpretation of the Born or Everett wave function. P.S. Why didn't Einstein use this argument? He wasn't sure about the reality of gravitational waves and assumed only the presence of hidden parameters.° --------------------- *) - By the way, a "smile" without a cat can be detected according to Einstein's equations. Raising one of the indices, substituting I=k and summing, we find: R=-(8πG/c^4)T, where T=T(n) is the trace of the energy-momentum tensor (~ "gravitational memory."). **) - If the cat is replaced with a detector, then with each absorption its state will change (which makes measurement possible). It is clear that this will also cause additional radiation of gravitational waves, since the included detector is already a source. ***) - The formula can be given in the following form for a photon: I(G)={[w/w(pl)]^2}ħw^2. Of course, this approach is also applicable to the case of entangled particles. °) - Frame of reference in GR: 0."In the general case of an arbitrary variable gravitational field, the metric of space is not only non-euclidean but also changed with time. This means that the relationships between different geometric distances change over time. As a result, the relative position of the "test particles" introduced into the field in any coordinate system can not remain unchanged." ( Landau-Lifshitz, II). 1.It turns out that since the Big Bang, all the particles in the universe speak, hear and listen to each other in the language of gravity (= irreducible spontaneous measurement). 2.Finally, the result of the measurement is a change in the state of the measuring device, a change in the physical /biological state of the observer, a change in the mental / intellectual state of the observer, that is, the detection of the next phase of evolution its own frame of reference; - thanks to which measurement becomes possible.

[@drast1cone42]

The photons are not in superposition. You have millions of photons in different alignments. You are simply measuring the alignment in masse. No one photon is in both positions.

[@schmetterling4477]

Almost. The important realization one has to make is that "a photon" is the outcome of a single quantum measurement. It does not even exist in the free electromagnetic field. If you identify photons with the outcomes of dice throws, then you are ontologically on the safe side.

[@DelfinaKS]

I love how you explain complex ideas in simple language. Thank you for clearing the misconceptions in pop culture. I still can't understand why great scientists like Schrodinger though it would make any difference if the measurement is done by Geiger counter, a cat, or a human. I really can't understand how any one who has common sense, least of all someone who studies science, would think that partials fundamentally behave differently if a machine or cat or a human measures it. A measurement is a measurement no matter who does it!

[@FrancoisEustache-ed6gd]

My own take on the Schrodinger's Cat experiment is that it uses the expression ''observer'' in the anthropomorphic meaning. The decay detector is a mecanism that will really observe the collapse of the superposition state and will kill or not the cat. The human observer is just in his own state of ignorance until he open the box or smell the dead cat without opening the box.

[@schmetterling4477]

Schroedinger was trying to do the right analysis but he didn't quite get there. The important difference between CLOSED and OPEN boxes is the reversibility of energy flow. I don't believe he actually noticed that. A measurement is, BY DEFINITION, an irreversible energy flow. One can simply not perform a measurement on a truly closed system (like the stated box). Without that measurement no knowledge of the contents is possible. This is an entirely classical result, though, and one can discuss Schroedinger's cat with perfectly classical physics, if needed. The correct tool would have been the Poincare recurrence theorem, which Schroedinger must have known about.

[@alfadog67]

I get it now. Eureka! Quantum Mechanics is simply a probabilistic tool. It's nothing more than a framework to calculate probabilities. Schroedinger realized how ridiculous it was to view natural world as the tool sees it, so he demonstrated that it wasn't about "quantum" specifically, but about probabilities, like his cat's status. I can use your model to create a probability wave that answers "was the polarity x or y?" or "will the bus be on time?". Classical descriptions are deterministic, while quantum-mechanical descriptions are probabilistic.

[@schmetterling4477]

The problem is that quantum mechanics CAN NOT be probabilistic. Why? Because random numbers do not satisfy any of the physical conservation laws, but quantum mechanics does. So, NO. Quantum mechanics is NOT about probabilities. It is about relative event frequencies in repeated experiments, but it turns out that probabilities of random events are only one solution to the axioms that such systems have to obey (by definition). Most people have simply never outgrown the determinism/randomness false dichotomy fallacy. And, no, this is not new. con Neumann had this figured out in 1932, already. Welcome to your world, which is stuck in a mental loop that was already wrong almost 100 years ago.

[@charlesprabakar]

Interesting - and as much I agree with your experimental explanations (except for couple of nuances) - however in my view, the whole point of the Schrödinger’s cat thought experiment, (especially according to Schrodinger's communication with Einstein and others) was to drive home the point that QM is incomplete (and not to interpret the TE literally)! This brings me to our theory’s alternate explanation using our Riemann hypothesis meta proof function called CPT(α,Φ) function. as it has a twist to it! For example, under our theory, the whole classical universe (including us as humans and the “Schrodinger’s cat including its box”) gets birthed from quantum reality (at Planck's scales) again and again, every moment by moment! Since it occurs at close to speed of light we will never even realize it, especially after decoherence kicks in! So, in that sense, every one of us (including Schrödinger’s cat) are simultaneously both dead and alive only - meaning - we are continuously alive (from quantum reality standpoint) however we are only discretely alive from classical reality standpoint. In other words we are clinically dead for a “fraction of a moment“ when the classical particles get born again by shifting into the next Hodge lattice ( thus giving us a feeling of Muybridge’s Horse in Motion) as explained in the following article in detail When we think about it, this shifting into next lattice occurs for every137-n cycles of each particle - and so it is during that fraction of a moment is only the particle is in superposition mode between 0 degrees and 360 degrees of every cycle However when we measure it it (using current devices) it toggles immediately to either to 90 degrees or 0 degrees as you had correctly explained However, under our theory we have hypothesized that we may be able to measure the intermediate angles using the coordinates of Riemann sphere, provided we use Riemann zeta function as the correlation function - pending our experimental proof) This brings us to your experimental demo As you you had alluded , I also agree that the phase of photons will vary depending upon which angle the laser is turned However an additional implication of our theory is that every photon that gets birthed from the laser device also propagates only by the continuous annihilation of electron/positron pairs (multiple times) before it reaches the filter (as visually shown by our theory’s simulation mapping to Conway’s game of life in 1:21m of this clip (kzbin.info/www/bejne/eWPZmHx5m7aUrac) Now during the experiment, assuming everything happens at steady state - Scenario 1 When the light start going through the filter, the photons can be any phase( say 76 degrees) - however when it enters the filter, it immediately tilts to 90 degrees as far as the observation of our eye senses In other words - since there is only one output beam, there is no possibility of cross interference Scenario 2 Let us imagine two laser beams with two filters ( equivalent to double slit experiment), then we will see alternating dark and light regions on the distant screen( similar to the double slit experiment) The dark and light regions are produced by “electron/positron pairs from the output beam from the first laser ” interfering with that of the second laser - and vice versa - thus getting shifted as multiple bands ( Note : The traditional classical explanation is the crest of one wave of light overlaps with the crest of another wave I.e. the two waves combine to make a bigger wave and you see a bright blob of light. Similarly when the trough of one wave overlaps with the crest of another wave, the waves cancel each other out and you see a dark band) I know it is totally a new type of explanation- however it is based on sound math principles as explained in this article below And if I may explain it visually using Conway’s game of life First - Under our i-TOE model, the classical reality gets birthed from the quantum reality -- and better yet, every one of the classical latticed particles get birthed from the 4 complex conjugated quadruples of the 8 quantum latticed rings (as per our 5th RH proof), before landing on to the next lattice of its taurusized hodge latticed classical model (aka Hilbert’s countable ∞ hotel/Banach-Tarski/Russell's paradox), so that gauge gravity can emerge by them orbiting smoothly like the frames of Muybridge’s Horse in Motion. More specifically, as visually shown in this simulation, this is how every particle and antiparticle pairs from the quantum reality gets annihilated before birthing their classical equivalent particles(muons, photons gauge bosons etc) so that gauge gravity can emerge by them all orbiting smoothly on their unique geodesics like the frames of Muybridge’s Horse in Motion using the following mapping -- Conway’s rule ”any live lattice with fewer than 2 neighbors dies” mapped to our i-TOE’s rule χ(1 mod 4) = 1. (Note: Mathematically, this is equivalent to the complex conjugates of the Gaussian integer factors of the particle/antiparticle pairs of quantum lattices collapsing to birth its classical equivalents, as respectively/visually depicted in 1:21m of clip below and 21:25m of this clip(lnkd.in/g4557Vh4) -- Mapping Conway’s rule “any live lattice with 2 or 3 live neighbors lives” to our i-TOE’s rule χ(3 mod 4) =-1 -- Mapping Conway’s rule “any live lattice with more than 3 neighbors dies” to our i-TOE’s rule χ(2 mod 4) =0 To understand how this works, read my article/paper in preprint (www.linkedin.com/pulse/summary-our-firms-10yrs-toe-work-wa-request-world-form-prabakar-k25sc/?trackingId=HMyXjPicQRm4hcSYi3FT2g%3D%3D) Welcome complementary POVs…..

[@JrgenMonkerud-go5lg]

basically for the classical limit to hold, given that light in classical electrodynamics also superposes linearly, it has to be true that for any light what so ever, the classical behavior has to hold for intensity as giving probabilities in all cases, only when detectors and interactions that are inelastic are involved does anything that doesnt happen in classical electrodynamics happen. even a single photon state, which isnt really a coherent concept but anyway, the intensities given by some waveform of classical light to hand you a probability current in a sense, works out fine, it has to because otherwise you would never get back to classical radiation at large N. so i just very severly doubt there is any reason at all to think of light as traveling as particles at all.

[@eternaldoorman5228]

A measuring device only measures a _measurable_ quantity though, and a probability, even if it is 1, i.e. a certainty, is not actually something you can measure directly without doing a large number of measurements and gathering statistics that represent the measured values. The super-position states can therefore never be known impirically. So when you say that "we" know the cat is both dead and alive, that is not impirical knowledge, it is deductive inference based on the theory that quantum states in a Hilbert space have some sort of physical reality independent of the actual observations that are made in a laboratory. To me this makes good sense, and it shows that the wave-function collapse is a condition of impirical knowledge. We simply cannot make sense of a measuring device that gives self-contradictory readings when used to measure some states of a system. But it is hard to make such an argument when the lecturer freely switches between speaking about a state of the system and a measurement as if these two things are identical!

[@undercoveragent9889]

I reckon that Schrodinger's cat would rather be someone else's cat.

[@JrgenMonkerud-go5lg]

so to summerize, in the examples with light, a classical hidden variables model involves proposing a set of classical states that evolve independently, with some dynamics that applies to all of them, then sum over those initial conditions to obtain the correct probability distribution that also results from the quantum mechanical treatment. if you assume the hidden variables associated with probabilites of detection of said light are deciding whether to absorb or not at the detector, and the dynamics of the light in transit is pretty much the same wavepattern in all the hidden variables states, then there is no mystery in any of these cases, the wave interference are simply interference of waves in real space, that results in probabilities for absorption at some detector, then the hidden variables, in the cases you outlines, only have to account for when in a specific run, you get detections in detectors, based on the intensity and frequency at that detector, and the argument you put forward to say there was no such thing as predetermined outcomes all along, doesnt apply, since the dynamics of the interference were moved from the superpositions of quantum states to just being the results of dynamics of waves. these examples are done with a huge number of photon states in the light, so this argument has to be true, but if you review it carefully, it has to be true for single photon states as well, or we lose the classical limit.

[@markmuller7962]

I wanted to click on the previous thumbnail but I couldn't because I was at work and now I've clicked on the new thumbnail and I'm sad

[@George4943]

A filter changes polarization. That is how we know the light is all of a single polarization. The 3 filter experiment is simple. Filter A polarizes, now put filter B at 90 degrees. At this point no light at all gets through. Now put filter C at 45 degrees to both between them. Suddenly light gets through. This experimental result is explained by quantum theory, and not by lack-of-information theory.

[@JrgenMonkerud-go5lg]

the wave picture for light is imo completely superior, and the collapse that is necessary to account for entangled states for instance is in good agreement with the principles of a more general hidden variables picture of the dynamics of fermions as well. and i have to stress, it is not inconsistent with any predictions of quantum mechnics, and is possible to modify into a local form, which can be directly tested and compared with quantum field theory.

[@jamie9060]

Is there any experiment that could demonstrate the quantum mechanics explanation this video provides? Results that would show the polarized light is a non-collapsed superposition of two vectors (instead of the more straight forward explanation that any vector in R2 has 2 components (x and y) and removing some amount of either component changes the vector direction and magnitude? Mathematically, I do not believe there is any difference between these two explanations. Using a linear combination of two vectors (a superposition of those vectors) versus just using the actual vector which has components x and y. I cannot think of any experiment that would demonstrate a QM “collapse” instead of ordinary vector maths. (Obviously these polarization filters do more than just remove vector components. The filter placed in a light wave will generate its own fields and these fields may rotate the laser light’s polarization and/ or interfere. But keeping things simple and assuming the filter is simply a perfect filter that only removes one directional component from the light which passes through it.

[@tumultuouscornucopia]

So, at the beginning you insist that the cat REALLY IS in a superposition until you open the box, and you say you're about to explain how we KNOW that. And by the mid point you have carefully gone through all the reasoning that proves the superposition has disappeared long before the cat gets involved. What am I missing here ?

[@DaviddeKloet]

Do you reject Everett's many worlds interpretation?

[@ShonMardani]

Does the first filter cuts the laser light intensity by half?

[@schmetterling4477]

That's not really what these filters do. They partially absorb energy AND they turn the direction of the polarization of the light that passes through. You need a 2x2 matrix to describe them correctly. A simple scalar absorption factor will not do. This is perfectly classical 19th century physics. I have seen versions of this in old German optics textbooks that wrote these matrix coefficients with Fraktur letters.

[@davidf2281]

13:01 I don't understand how simply rotating the entire experiment through 45 degrees and getting the same result as before proves anything at all?

[@TimoBlacks]

It doesn't. That's why you don't understand it. The issue is her demonstration, not you.

[@PeterSingh-qe8cc]

Measurement. How would you identify the precise moment the cat died? The precise moment the cat is alive, and the precise moment the cat is dead. Would there not be a moment when both alive and dead states coexist?

[@TimoBlacks]

You can't know precisely when it died. And it did not die. It was in superPornoPosition. Then the moment you look, is the moment it dies or lives. Before looking, the 69 position is in full effect.

[@schmetterling4477]

The cat is never truly alive in a closed box. Life is a phenomenon that requires constant energy and matter flow. Schroedinger simply picked a really crappy example to make a point about quantum mechanics that turns out to be DIFFERENT from his own failed mental model.

[@siarez]

The outcome of your polarized light experiment is completely consistent with Maxwell's equations. It doesn't prove that anything quantum mechanical is going on. To prove anything quantum mechanical is going on you should shoot ONE photon at a time. That's only when Maxwell's EM produces a different prediction than quantum mechanics.

[@edwardlazell3157]

So for the double slit experiment, if ignorance rather than superposition were true, would we still see the wave pattern on the back wall, but only half as bright? I ask because with the orientation experiment, ignorance of light's state would mean we expect only half of the light getting through instead of all of it.

[@schmetterling4477]

For the double slit experiment you aren't seeing anything related to quantum mechanics. You can do it with water waves and get the same qualitative outcome. You can also easily see that Planck's constant doesn't show up in it anywhere, which kind of defeats the purpose of finding a quantum effect.

[@ed.puckett]

I disagree that a mixed state of two pure physical and opposite states is both this and that. The mixed state is a separate state altogether, and it is nonphysical. It becomes this or that when measured.

[@Krisoler]

The idea of ​​superposition of states (vertical, horizontal) is very arbitrary because in reality we could choose any other pair of orthogonal orientations within an infinite number of orientations between 0 and 2*Pi, and then we would speak of a quantum particle having an infinite number of superimposed states! It seems to me that the idea of ​​superposition is simply a functional mathematical artifice but not a satisfactory explanation. My very personal interpretation is that the light coming out of a polarizer actually comes out with the polarization angle given by the polarizer, and when the light reaches another polarizer with the same angle it simply will not be affected, however when the light reaches a third polarizer with a different angle then the polarizer deviates the polarization orientation of the wave to that of the polarizer itself, letting it pass, or to the perpendicular direction and rejecting it, but it does so in a probabilistic way, that is to say, it is the measuring device that causes a probabilistic change in the polarization direction of the light, something similar to an antenna that can transmit or reflect a radio wave, in what is called the directionability of an antenna.